094
ACUS01 KWNS 121632
SWODY1
SPC AC 121631

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1131 AM CDT Wed Jun 12 2024

Valid 121630Z - 131200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
NORTHERN MINNESOTA AND ADJACENT NORTHWESTERN WISCONSIN AND WESTERN
LAKE SUPERIOR...

...SUMMARY...
Scattered severe thunderstorms capable of very large hail, damaging
wind gusts, and a few tornadoes will be possible across parts of the
Upper Midwest late afternoon and early evening.

...Upper Mississippi Valley/Upper Midwest...
Bands/clusters of convection are ongoing at this time, from the
Minnesota Arrowhead southward across northern Wisconsin, and
southwestward across southern Minnesota into the Mid Missouri Valley
region.  This convection continues moving eastward, toward a less
unstable airmass, which should temper severe risk over the next few
hours.  Greatest potential for a couple of marginally severe storms
appears to exist over southwestern Minnesota and adjacent portions
of southeastern South Dakota and northwestern Iowa, where the
greatest instability resides.

Greater severe risk is forecast to evolve later this afternoon,
north of the ongoing storms.  Here, daytime heating ahead of an
advancing cold front (associated with a low-amplitude short-wave
trough embedded in fast westerly flow aloft, and moving eastward
along the international border) will result in moderate to strong
instability (2500 to 3500 J/kg mixed-layer CAPE) within the
pre-frontal warm sector.

Weakly veering but strengthening flow with height across the region
will provide favorable shear for organized/rotating storms.  Initial
convection -- expected to initiate in the 12/20Z to 12/21Z time
frame -- should quickly organize/become supercellular, with very
large hail likely to be the initial/primary severe risk.  A couple
of tornadoes will also be possible, though veered low-level flow
should temper overall tornado risk.  With time, storms are expected
to cluster/grow upscale, with small-scale bowing expected, which
should yield a gradual increase in damaging-wind potential.  Storms
will spread rather quickly eastward/southeastward with time, with
some severe risk likely to linger through the evening before
gradually diminishing overnight.

...South Florida...
Widespread convection is ongoing across southern Florida, within a
zone of low-level warm advection south of a weak cold front lying
across central portions of the Peninsula.  Modest lapse rates aloft,
but a very moist/tropical boundary layer is resulting in deep CAPE,
which will continue to support the widespread convection.

While mid-level flow remains rather weak, flow veers/increases with
height through the lower troposphere.  This is providing ample shear
for generally weak/transient updraft rotation.  Given the associated
potential for a brief tornado or two, low (2%) tornado
probability/MRGL risk is being introduced across portions of South
Florida.

For additional short-term information, please refer to SWOMCD #1237.

..Goss/Moore.. 06/12/2024

$$